The Unseen Effects of Habitat Loss

Whilst climate change continues to hog the limelight, habitat loss remains the key threat to biodiversity worldwide. And whilst events like the Australian bushfires obviously contribute to habitat loss, its main cause is land clearing, whether for agriculture, cattle grazing, mining or urbanization. No matter how many politicians deny or try to deviate attention from it, scientists have shown time and time again just how threatening habitat loss is to our planet’s biodiversity.

On the surface, the process seems quite simple. Habitat goes away, animals lose shelter and food. Yet this is just the tip of the iceberg. Many processes take place below the surface, cascading through an ecosystem. So let’s have a look at the manifold effects of habitat loss, and why it’s the greatest threat to biodiversity today.

What is Fragmentation?

Imagine the continent is an ocean, and every area of native vegetation is an island. If you are a lizard, your habitat is limited to the island you exist on, and whichever islands are close enough for you to reach. Yet if a couple of those nearby islands are suddenly destroyed, your food, shelter and mating options are suddenly limited to what that one island has to offer. If a disease breaks there, there is nowhere to escape to. If a new neighbor arrives and eats all your food, takes your shelter or even finds you and your friends make good dinner material, well… you are done.

That’s the danger that land clearance or change poses to species that live in an extremely fragmented landscape, where habitable areas are scarce and isolated. It doesn’t necessarily mean the death of all species, of course. Some have the ability to adjust to changes, and land change does’t always mean that land becomes inhospitable. But generally, land clearance does lead to a net negative effect on an ecosystem.

These ideas are the basis for the concept of habitat fragmentation, the breaking apart of habitat, which is usually a direct consequence of deforestation and land clearing. It deals with how the structure (shape, size and disposition of elements) and complexity (types of elements) of a landscape change in time and space, and how species living on that landscape respond to those changes. A landscape is composed of everything from rivers to housing, farms to forests. And whilst we’re generally referring to human-caused fragmentation here, there are plenty of examples of natural fragmentation. Trees falling, seasonal fires*, rivers, mountains, all create some level of fragmentation in landscapes. That means that, as often is the case, fragmentation and landscape change are natural processes that are being exacerbated by human activities beyond species capacity to respond and adjust.

A landscape, in that context, can be as big as the entire Australian outback, or as small as your garden. It all depends on who is looking, or to be clearer, what species are we thinking about. From the eyes of an ant, your garden is a diverse and complex environment, with places where to eat, places where they are exposed to predators and places where to build their houses. For a possum, a park is similar. For a migratory bird, maybe the whole continent, or two different landscapes (one for each life stage) works on this level.

Why is Scale So Relevant?

The responses to habitat fragmentation are diverse and many times controversial. A long term fragmentation study in eucalyptus forests in New South Wales (the Wog Wog Habitat Fragmentation Experiment) showed that eucalyptus forests are actually resilient to fragmentation. Yet it also showed that skink bodies are in average smaller in fragmented areas and that fragmentation disrupts the infection of skinks by parasites. On the other hand, a long term experiment in Amazonia showed impoverished flora diversity in fragments, and significant changes in microclimate after fragmentation. Overall, the exact impacts of habitat fragmentation on biodiversity are hard to predict, but it is evident that it promotes changes that go way beyond habitat loss.

The views from Hanging Rock (Victoria, Australia, top) and Serra da Mantiqueira (São Paulo, Brazil, bottom). Both show degraded landscapes with patches of remaining forests, pastures and human settlements. (Image Credit: Marina Schmoeller, CC BY 2.0)

The views from Hanging Rock (Victoria, Australia, top) and Serra da Mantiqueira (São Paulo, Brazil, bottom). Both show degraded landscapes with patches of remaining forests, pastures and human settlements. (Image Credit: Marina Schmoeller, CC BY 2.0)

Just the other day, I went on a hike (or bushwalk) at Hanging Rock, a volcanic mountain about one hour away from Melbourne. At the top, there is a magnificent view of the surroundings… and a clear picture of a very severely fragmented landscape. It brought me a bittersweet taste of my home in Brazil. I see something similar whenever I hike in Serra da Mantiqueira, the mountain range where my hometown is, in the Brazilian Atlantic Forest. What I see when I look down to the valley below? 500 years of intense deforestation and forest fragmentation, with only mountain tops and very steep hills still forested. The similarities do not stop there. A study by Beyer and collaborators combined metrics of habitat loss, quality and fragmentation to show how intact the world’s ecoregions are, and eastern Australia loses to eastern Brazil by little. But here is the difference: while deforestation in the Atlantic Forest has mostly stopped, eastern Australia is making an effort to catch up. In the state of Queensland, even after the Environment Protection and Biodiversity Conservation (EPBC) Act came to be in 2000, land clearing continued to rise. To fully understand the scenario, the Australian State of the Environment Report is a useful resource.

What Can Be Done?

Political instability has played a major role in regulating land clearance rates over the past decades, because cycles of government change legislation and how well enforced it is. Lack of enforcement is key. How many people are on the ground protecting the remaining native vegetation? How much equipment and technology are provided to monitor landscape change? All that depends on a large part on government, and it is our job to make sure our representatives care about it. The review of the EPBC Act in Australia is a big opportunity to make sure environmental laws get stronger and are properly enforced, to reverse Australia’s escalating land clearing rates.

We need to seek and set in motion initiatives that effectively reduce biodiversity loss. Indigenous people, traditional communities, farmers, everyone must be included in the decision, because everyone is living in and transforming their landscape. We must value the contributions each one has to offer and rise up to the challenges each must face. We have lost too much already.

*Natural in many ecosystems, but not in all of them and only up to a certain frequency and intensity.

Marina Schmoeller is an ecologist, conservation biologist and sustainability enthusiast. She is currently pursuing a PhD in understanding the effects of landscape change in biodiversity. You can follow her on Twitter here.

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